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Current studies were undertaken to compare the genomes of Kirsten murine sarcoma virus (Ki-MuSV), Harvey murine sarcoma virus (Ha-MuSV), and the replication-defective endogenous rat virus to understand the function of these viral RNAs. Genome organization and sequence homology were studied by fingerprinting large RNase T1-resistant oligonucleotides and by cross-protecting homologous oligonucleotides against RNase A and T1 digestion with complementary DNA prepared from each of the other viral RNA. Ki-MuSV and Ha-MuSV were found to share an extensive series of rat-derived oligonucleotides begining ca. 1 kilobase (kb) from the 3' end and extending to within 1.5 kb of the 5'end of Ki-MuSV RNA. The total map distance covered in ca. 5.5 kb. The eight oligonucleotides covering the 1.5 kb at the 5' end of Ki-MuSV RNA were not found in Ha-MuSV RNA. Five out of these eight oligonucleotides, however, could be designated with certainty to be of rat virus origin. Since Ha-MuSV is 6.5 kb in size and Ki-MuSV is 8 kb in size, the major difference between them is the 1.5 kb from the replication-defective endogenous rat virus sequences at the 5' end of Ki-MuSV not present in Ha-MuSV. Consistent with the difference in the genome structure, these two sarcoma viral RNA'S yielded distinct major translation products in cell-free systems, I.E., A 50,000-dalton polypeptide (P50) from Ki-MuSV and a 22,000-dalton polypeptide (p22) from Ha-MuSV. These polypeptides may provide the necessary protein makers for identifying in vivo virus-coded proteins.
Shih et al. (Sat,) studied this question.